It is known to place one or more packers in a wellbore to separate zones above the packer from zones below. Resettable packers are known that can be set for a single operation, then be released to move in the wellbore for removal of the packer and associated tools therefrom, or moved within the wellbore to be set at another location for a subsequent operation.
It is also well known to complete or line wellbores with liners or casing and the like and, thereafter, to use resettable packers to separate the wellbore uphole and downhole of the packer, such as to direct treatment fluids, for example fracturing fluids, through flowpaths created through the casing to reach the formation therebeyond.
Conventional methodologies for creating flow paths include perforating the casing using apparatus such as a perforating gun which typically utilizes an explosive charge to create localized openings through the casing and or abrasive jetting for eroding openings therethrough. Alternatively, the casing can include pre-machined ports, located at intervals therealong. The ports are typically sealed during insertion of the casing into the wellbore, such as by a dissolvable plug, a burst port assembly, a sleeve or the like. Thereafter, the ports are typically selectively opened by removing the sealing means to permit fluids, such as fracturing fluids, to reach the formation. Typically, when sleeves are used to seal the ports, the sleeves are releasably retained over the port and can be actuated to slide within the casing to open the port. Many different types of sleeves and apparatus to actuate the sleeves are known in the industry.
Treatment fluids are directed at high pressure into the formation through the open ports. At least one sealing means, such as a resettable packer, is employed to isolate the balance of the wellbore below the treatment port from the treatment fluids. In U.S. Pat. No. 6,394,184 (Tolman) to Exxon, a resettable packer, as part of a bottom hole assembly (BHA), is set below perforations. A circulation port sub, above the packer, provides a flowpath to wash debris from above the resettable packer to aid in releasing the packer or to inject treatment fluid to the formation.
Further, in some known methodologies, using tubular strings having sleeves for initially blocking treatment ports, the BHA includes a resettable packer that is also used to both shift the sleeve and seal below the treatment ports including: to engage and seal to a sleeve for shifting the sleeve open such as taught in U.S. Pat. No. 6,024,173 (Patel) to Schlumberger, or in combination with a locator, key or anchor to engage seal and shift the sleeve U.S. Pat. No. 1,828,099 (Crowell) and Canadian Patents 2,738,907 and 2,693,676, both to NCS Oilfield Services Canada Inc.
In the BHAs having resettable packers, it is known to provide equalization valves in the conveyance string or in the BHA for releasing a pressure differential across the packer to aid in its release and to permit movement of the BHA within the wellbore. Equalization valves are generally situated within the BHA to allow fluid to bypass the packer through the structure of the BHA itself. Both U.S. Pat. No. 6,394,184 (see Col 13, 14) and CA 2,693,676 disclose equalization valves wherein equalization fluid flow is directed through the BHA.
Further, the typical resettable packer is actuable in combination with a mechanical indexing mechanism, such as a J-slot apparatus, using uphole and downhole axial manipulation of the conveyance string to shift the resettable packer between an actuated, sealing position and reset positions. U.S. Pat. No. 6,394,184 (Col 15) and CA 2,693,676 disclose J-slots for actuating and de-actuating resettable packers, as well as the use of equalization valves. A packer element is located on a mandrel that is telescopically fit into a housing. The telescopic action alternately compresses and releases the packer element therebetween. The mandrel is fit with a J-slot component that operatively engages a corresponding second component within the housing. To equalize pressure above and below the packer, fluids must pass through the mandrel and housing to bypass the packer element.
When actuated, the packer element is axially compressed to radially expand into sealing contact with a surrounding tubular. Typically, actuation of a packer is contemporaneous with setting of an anchor to the tubular, such as through a tubular cone driving slips radially outwardly into engagement with casing. When axial compression on the packer element is released, the expectation is that the packer element will retract radially and release from the tubular. Similarly, the anchor's cone is released from the slips, freeing the housing for movement within the tubular. The nature of known J-slots mechanisms requires axial movement to shift the indexing status of the J-slot, typically involving some axial force on the packer element whilst still actuated and engaged with the tubular, potentially damaging the packer element.
Efforts are being made to minimize packer element damage, including washing debris from about the uphole end of the packer and equalization of pressure differential across the packer before de-actuation, however packer failure is still a reality. Thus there is interest in apparatus and methods to further address this issue.